Presented by: Mr Lucas F. ChaukeDr Azwianewi B. Makhado

Dr Jonas Mphepya

Climate change: potential impacts on marine ecosystems of South Africa

and in the Southern Ocean

Coastline stretches more than 3 000 km from the west by Atlantic Ocean, Indian Ocean (east), and the Southern Ocean (south) contributing to the differing climates experienced in these regions. This makes South Africa’s environmental conditions to be characterized by different oceanic dynamics.

Impact of climate change

• Climate change has been a “buzz word” for a while but its impact is now noticeable.

• Climate change is affecting marine ecosystems and is expected to continue to affect fisheries and other ecosystem services

Ice Plateau at Marion Island

Drivers of change

Recent changes have been observed in South African marine ecosystems.

The main pressures on these ecosystems are fishing, pollution, ocean acidification, habitat alteration and destruction, species invasion.

Some of these can be linked to climate change e.gthrough changes in ocean temperature, chemistry ocean circulation, stratification and nutrientavailaibility, eutrophication

Global trends in oceans

a) Ocean warming

Change in temperature of the upper 700 m of the global oceanSource: Intergovernmental Panel on Climate Change

Black, red and green curves are from different analysesGrey shading and red and green bars show 90% confidence intervals

Global trends in oceans

b) Sea level rise

Annual averages of global mean sea levelSource: Intergovernmental Panel on Climate Change

Red reconstructed; blue coastal tide gauge measurements; black satellite altimetry

The main cause of sea level rise is melt of ice, with heating and expansion of sea water also important

Ocean acidification

Present day sea-surface pH (left) and estimated change in sea water pH caused by human-created CO2 between the 1700s and the 1990s (right), from the Global Ocean Data Analysis Project and the World Ocean Atlas. The Southern Ocean and the North Atlantic Ocean have

experienced high rates of acidification

Ocean acidification refers to the ongoing decrease in the pH of the Earth’s oceans, caused by the uptake of anthropogenic carbon dioxide (CO2) from the atmosphere. Between 1751 and 1994

surface ocean pH is estimated to have decreased from approximately 8.25 to 8.14

Important regions for top predator breeding in

southern Africa

There are indications of recent cooling on the West and South coasts and warming on the East

Coast over a period of 20–30 years.

The shelf waters slightly further offshore south are slightly warmer, which could be due to the leakage of Agulhas Current and Agulhas Bank water to the Atlantic Ocean

Biodiversity indicators

Globally

South Africa

Critically Endangered

Endangered

Vulnerable

Near Threatened

Least Concern

Indicators such as the Red List index (based on IUCN red list classifications) have been used internationally to track the conservation status of groups of organisms. The example below (from BirdLife International) shows that globally the conservation status of seabirds deteriorated more rapidly than that of some other groups of birds. South Africa’s seabirds (many endemic to southern Africa) are not an exception to this trend – two thirds are classified as Threatened or Near Threatened (right)

Long-term changes in South Africa’s marine resources

African Penguins at Dassen Island – ca. 1930

photo C Kearton

Major breeding localities of top predators in the Benguela

ecosystem

Cape fur seal

There have been massive changes in distribution in the last 20 years (new colonies etc), population status remained relatively stable, and growth of new colonies have largely compensated for declines at other colonies (e.g. colonies in southern Namibia).

And there was also a significant northward shift in the distribution of the breeding population and was extended by ca. 680 km (from Cape Cross to Baia dos Tigres in Angola) whereas the eastward range of the breeding population remained constant throughout the time series.

The potential availability of prey such as horse mackerel Trachurus trachurus capensis for top predators may have influenced such distribution

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South-east displacement of forage fish species

In the 1990s, adult stocks of South Africa’s two most important forage fish species shifted their distributions from the west coast to being mostly east of Cape Agulhas. The northernmost fish processing plant at Lambert’s Bay was

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Seabird responses to changes in the distributions of some prey species

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Roseate Tern

Large decreases for species that compete with fisheries for prey but have inflexible

diets and are unable to adapt locations of breeding

Stability for species that do not competing with fisheries for

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Increases for species that compete with fisheries for

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Roy et al. 2007

Long-term change at sub-Antarctic Marion Island

Temperature trends

in the sub-Antarctic

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Marion Island shows the strongest

warming trend (0.21oC per decade, R2 =

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Individual station data from these locations

thus appear representative for larger

regional trends

Inshore-breeding seabirds

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Gentoo Penguin Crozet Shag

Numbers of Crozet Shags (left) and Gentoo Penguins (right) breeding at Marion Island have shown similar decreasing trends – both are benthic feeders eating similar prey.

The congruent trends suggest possible ongoing change in the benthic marine environment. Regionally the Crozet Shag is Critically Endangered and the Gentoo

Penguin is Endangered

Crested penguins

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Macaroni Penguin

Numbers of both species of crested penguin breeding at Marion Island have decreased – the Southern Rockhopper Penguin is regionally Endangered; the Macaroni Penguin is

Vulnerable

Southern Rockhopper PenguinMass of Southern Rockhopper Penguins returning to breed from overwintering grounds (where they spend six months) has decreased: a) males, b) females. This was not the case for Macaroni

Penguins, for which disease at large colonies contributed to decreases

Overwintering distributions of crested penguins in the South Indian Ocean (collaboration with France)

Macaroni (red and pink lines), Southern Rockhopper (yellow and white) and Northern Rockhopper (green) Penguins. Locations: Marion (circle), Crozet (triangle), Kerguelen

(lozenge) and Amsterdam (square) islands. Macaroni and Southern RockhopperPenguins at island groups have different winter feeding grounds

Divergent trends of Phoebetria albatrossesAt the Prince Edward Islands Sooty Albatross has decreased, Light-mantled

Albatross has increased

Light-mantled Albatross Marion: + 6% p.a. since 1996

Sooty Albatross Marion: – 2% p.a. since 1996

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Sooty Albatross Light-mantled Albatross

Positions at sea for birds from Prince Edward Islands

Sooty Albatrosses have a more northerly at-sea distribution than Light-mantled Albatrosses, which makes them more susceptible to by-catch mortality in long-line fisheries that operate in

the south Indian and Atlantic Oceans and off South Africa. This probably resulted in the divergent trends of the two species

At sea distributions of Phoebetria albatrosses

Spatial management of oceans expected to play an important role in biodiversity conservation

Controlled zone light grey; restricted zones dark grey

The Prince Edward Islands Marine Protected Area was proclaimed in April

2013

• In the Southern Hemisphere, there have been poleward shifts and local declines for ice-dependent populations of Adélie Penguins breeding in the West Antarctic Peninsula but increases and a southward range extension of Gentoo Penguins, which do not depend on ice

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• It has been predicted that all colonies of Emperor Penguins north of 67–68°S could be lost when Earth's tropospheric temperature reaches 2°C above pre-industrial levels, with negative impacts on all colonies north of 70°S.

Population of elephant seal has not increased despite ceasation of sealing. In the southern ocean, seals dived to deeper depths when foraging in warmer waters.

Results from time-at-depth indices showed that both male and female seals spent less time at targeted dive depths in warmer water, and were presumably less successful foragers when diving in warmer water. Continued warming of the Southern Ocean may result in the distribution of prey for southern elephant seals shifting either poleward and/or to increasing depths, presumably increasing energy utilization while searching for prey.

Ecosystem resilience

ongoing contributions are made to global research aimed at determining thresholds for ecosystem resilience – e.g.

across a wide variety of species and ecosystems for which long-

term data were available (including South Africa)seabird breeding success

consistently decreased and became more variable when prey abundance fell below one-third of its maximum observed value

“We have not inherited this earth from our forefathers but borrowed it from future generations”

Ancient proverb